Aspects of various embodiments of the present invention are directed to wireless communications, and particular aspects are directed to wireless communications for both power and data transmission.
Many wireless communication systems employ transponders and base stations that communicate with one another. One type of transponder used in many applications is an immobilizer type of transponder. Generally, immobilizers use a coil that can be aligned with an antenna at the base station along an axis to achieve coupling. This coupling is used to control the operation of a circuit at a base station with which the transponder communicates, such as to immobilize an automobile ignition in absence of coupling with the coil (e.g., with the coil implemented in a key fob).
In many immobilizer systems, such as a vehicle ignition system, the immobilizer needs to be oriented in a particular manner in order to communicate with the base station portion of the system. For instance, most applications use cylindrical coils (antennas), one for the base station and one for the immobilizer. The coupling between the two antennas is strongly dependent on the orientation, and the maximum coupling can be achieved if both antennas are kept on the same axis (coaxial operation). If the base station antenna area is much larger than the transponder antenna, real coaxial operation is not necessarily needed, but the axis of the transponder antenna is desirably held close to a center axis of the base station antenna. These approaches are often limited to applications with a very small angular deviation and a correspondingly small dihedral angle, in a range of a few millimeters. Some approaches to achieving this orientation involves the physical placement of the immobilizer (and related housing and other components) into a physical apparatus or slot that aligns the immobilizer with the base station. For instance, with many automobile immobilizer applications, the immobilizer works via insertion into a slot that ensures that the immobilizer is correctly oriented relative to the base station.
Unfortunately, such alignment systems can be difficult to use, expensive to implement and otherwise limit the ability to readily implement transponder-based operations. For instance, free hand operation in which the car key fob is kept in hand or on a user's person has been limited, generally requiring that the user ensure that the fob is positioned correctly and is otherwise appropriately aligned. Regarding vehicular ignition operation, such systems can be particularly challenging to implement in a manner that permits secure operation while also ensuring operability in the event of power loss on the transponder.
These and other matters have presented challenges to the design and implementation of immobilizer systems for a variety of applications.